This invention relates generally to levers used for uncoupling railroad cars and more particularly to uncoupling levers of a telescoping type which extend and contract in response to movement of a cushioned railroad car coupler.
A railroad car uncoupling lever provides a manually operable means by which a person can uncouple adjacent railroad cars. One end of the uncoupling lever is connected to the car coupler mechanism and the other end of the lever, which includes a handle portion, is pivotally mounted by a bracket to the endsill of the railroad car. The simplest type of uncoupling lever consists of a steel rod bent into a particular configuration wherein one end of the rod hooks through an eye in the car coupler and the other handle end of the rod is pivotally mounted to a supporting bracket. However, such a simple lever is useful only when a constant distance exists between the coupler and the supporting bracket.
Cushioned railroad cars have couplers which are mounted on a center sliding sill which can move fore or aft as much as 20 inches in order to absorb buff and draft forces. In addition to the permissible fore and aft movement of the coupler, angular or side-to-side movement of up to 15 degrees from either side of a longitudinal center line may occur. This, of course, means that an uncoupling lever for such a car must be capable of extending and contracting as the distance between the coupler and the supporting bracket increases and decreases. The supporting bracket, which pivotally anchors one end of the uncoupling lever, may be mounted at various locations along the endsill of the car. This increases the range of distances over which an uncoupling lever must be capable of telescoping. When worst case conditions are taken into account, a telescoping uncoupling lever must be capable of substantial contraction and extension, viz. over the approximate range of 37 inches to 84 inches.
Various types of telescoping uncoupler assemblies have been developed. For example, U.S. Pat. Nos. 3,227,289 to Cseri, 3,258,133 to Hawkins, and 3,438,513 to Miller all disclose an outer tubular member having mounted to one end thereof a handle pivotally secured to the endsill of a railroad car. The other end of the outer tubular member slidably receives a smaller longitudinal member which is in turn connected either directly or indirectly to a railroad car coupler thereby defining a telescoping uncoupler assembly.
U.S. Pat. Nos. 3,239,074 to Boone and 3,814,267 to Chierici disclose telescoping uncoupling levers which more closely resemble the present invention in that each includes a longitudinal housing having two chambers which telescopingly receive two arms. The distal end of one of the arms has mounted thereto a handle pivotally carried by a bracket on the endsill of the car and the distal end of the other arm is connected to the railroad car coupler. Blocks or shoes are attached to the proximal ends of the arms for guiding the arms within the housing.
Although such telescoping uncoupling levers have solved some of the problems which such levers encounter, certain problems still remain. It is difficult if not impossible for such levers to accommodate the substantial range of distances over which an uncoupling lever must be capable of telescoping when worst case conditions are taken into account. The design of telescoping levers is further complicated because railroad operating conditions impose further restraints; for example, the necessity of designing a lever so that (a) a missed coupling impact will not damage the lever, and (b) clearance restrictions are not violated. If a telescoping uncoupling lever is subjected to a distance beyond its operating range, the tremendous forces transmitted to such a lever permanently deforms it rendering it inoperable.
Because of the way in which the sliding and stationary members of conventional telescoping uncouplers cooperate, it is possible for such a coupler to "lock-up" even though the operating range of the coupler has not been exceeded. This lock-up problem typically occurs at the beginning of a contraction after the coupler has been extended to near its maximum extended range. During this condition, there is a minimum of overlap between the sliding and stationary members in the telescoping section resulting in maximum axial misalignment between such members. Such misalignment tends to cause a binding frictional force between the sliding and stationary members which if sufficiently great prevents the movable members from sliding axially with respect to the fixed members, and the lever locks up or freezes causing the lever to be deformed by the compression forces. The present invention provides a solution to the lock-up problem and to the inability of levers to operate over the full range of distances encountered in worst cast conditions.